The present invention relates to an X-ray CT (computed tomography) scanner, and more particularly to the X-ray CT scanner having an automatic scanning mechanism which covers a series of operational sequences from the beginning to the end of a CT examination, which is especially favorable to mass screening.
Prior to diagnosis with an X-ray CT scanner, an operator places a patient in place on a patient couch and determines desired slicing planes, known as a positioning. A first positioning method uses a positioning light and a second method uses a scanographed image. In the former method, in which a tabletop having a patient is moved by hand, the positioning light is operated to point its light beams at a starting position of desired slicing planes by X-ray scanning. In the latter method, scanography can be made prior to diagnostic scan for obtaining the scanographed image on which desired slicing planes including its starting position can be specified.
After completing the positioning the tabletop is carried along the patient's body axis by means of an automatic sliding mechanism into an opening of a gantry to bring the starting position to an X-ray beam position in the opening. The scan is followed immediately by the tabletop being moved along the body axis.
During the diagnostic scan, the patient is required to stop her or his breathing to eliminate body motion artifacts. An instruction to stop breathing is currently given by an operator's voice or by sequential turn on or turn off of plural LEDs on the gantry.
On completing the diagnostic scan, the tabletop is drawn out and carried back to its initial position in response to an operation by hand, and the patient couch is lowered to bring the patient down.
However, in the above sequence of operations, the operator has to intervene by hand many times between operations directed by a console of the scanner. Such operations by hand include mainly the setting of the patient in place on a couch and the determination of slicing planes. These manual operations form a substantial part of the entire operation and require much operator's work, thus remarkably reducing the efficiency of the X-ray CT scan. This drawback is especially true of mass screening.
On the other hand, giving an instruction to stop patient's respirations by voice tends to result in failure, because the patient does not recognize a necessary time interval of respiration stop for the whole diagnostic scan. Though the above-said LEDs, which sequentially turn on or turn off, helps recognition of the respiration-stop time interval, it is not sufficient because an exact time cannot be shown on the LEDs.